The invention relates to a bead bundle intended for use in pneumatic tires, a method of making such a bead bundle, and pneumatic tires incorporating such a bead bundle.
In the construction of a tire, a bead ring provides reinforcement in the tire where the tire meets the rim. The bead ring is often made in the form of a bead bundle which comprises at least one (preferably one) strand of wire disposed in a plurality of adjacent annular turns which are wrapped with wire or another suitable material to hold the ends of the wire and the annular turns together. The ends of the wire or other wrapping material are ordinarily tucked under one of the wraps or knotted to retain the wrapping material on the bead bundle. Unfortunately, in the case where a wire wrap is used, when the bead bundle is deployed in a tire the exposed ends of the wire can sometimes, over time, cause a fault or tear to develop in the bead area of the tire, limiting the life of the tire. Also, when a wrap less stiff than wire is used, the knot used to secure the wrap can cause an imbalance in the weight distribution and gauge of the bead bundle and jeopardize the uniformity of a tire in which it is used. In both cases, when there are exposed free ends of wrap, or when the wrap is knotted, the ends of the knot may trap air in the area of the bead bundle during the building of a tire which may cause eventual delamination of the bead in the tire construction. Such defects are detectable on inspection, and such tires have to be scrapped.
Often, during the construction of a tire the bead bundle undergoes a deformation. It is believed that this bead deformation takes place when a tire construction is cured. Though not seriously detrimental to the operation of the tire, bead deformation substantially obviates the ability of the tire manufacturer to design an optimal bead shape and retain the optimized bead shape in an actual tire construction.
It is an object of the invention to provide a method of making a bead bundle and a bead bundle made thereby having improved uniformity and a construction that substantially eliminates the trapping of air in a tire construction. It has surprisingly been found in accordance with the invention that the method provides a bead bundle which is stable during the construction of a tire and substantially retains its shape during the curing of a tire.
It is also an object of the invention to provide a pneumatic tire using the bead bundle of the invention which has improved uniformity and endurance, and is made such that the number of scrap tires produced is reduced.